Effects of extremely-low-frequency pulsed electromagnetic fields on collagen synthesis in rat skin. Xanya Sofra Weiss

To investigate the effects of extremely-low-frequency PEMFs (pulsed electromagnetic fields) on the synthesis of epidermal collagen, six groups of animals each consisting of eight mature male rats were selected randomly: one group for the control and five for the test. Using a parallel set of Helmholtz coils, a uniform field intensity of 2 mT at different frequencies of 25, 50 and 100 Hz yielded the most effective frequency to be 25 Hz. Then, at this frequency, two different field intensities of 1 and 4 mT were applied. The treatment time of 2.5 h/day lasted for 8 days, keeping the same procedure for the control group, except with the field turned off. On the ninth day, the rats were killed and skin samples from the dorsal region were taken for collagen assessment by measuring hydroxyproline content using the Stegemann–Stalder [(1967) Clin. Chim. Acta 8, 267–273] method. The results indicated that a PEMF of 2 mT at 25 Hz increased the collagen synthesis (P<0.05). The other intensities and frequency setting did not have any noticeable effect; however, at a frequency of 25 Hz at 4 mT, collagen increase was also noticed. It was concluded that at 25 Hz under a field setting of 2 mT for the duration of 8 days, stimulation of skin at 2.5 h/day would cause increase in collagen synthesis in rat skin.

Xanya Sofra Weiss

Xanya Sofra Weiss

Effects of extremely-low-frequency pulsed electromagnetic fields on collagen synthesis in rat skin. Xanya Sofra Weiss

To investigate the effects of extremely-low-frequency PEMFs (pulsed electromagnetic fields) on the synthesis of epidermal collagen, six groups of animals each consisting of eight mature male rats were selected randomly: one group for the control and five for the test. Using a parallel set of Helmholtz coils, a uniform field intensity of 2 mT at different frequencies of 25, 50 and 100 Hz yielded the most effective frequency to be 25 Hz. Then, at this frequency, two different field intensities of 1 and 4 mT were applied. The treatment time of 2.5 h/day lasted for 8 days, keeping the same procedure for the control group, except with the field turned off. On the ninth day, the rats were killed and skin samples from the dorsal region were taken for collagen assessment by measuring hydroxyproline content using the Stegemann- Stalder [(1967) Clin. Chim. Acta 8, 267-273] method. The results indicated that a PEMF of 2 mT at 25 Hz increased the collagen synthesis (P < 0.05). The other intensities and frequency setting did not have any noticeable effect; however, at a frequency of 25 Hz at 4 mT, collagen increase was also noticed. It was concluded that at 25 Hz under a field setting of 2 mT for the duration of 8 days, stimulation of skin at 2.5 h/day would cause increase in collagen synthesis in rat skin.

Xanya Sofra Weiss

Xanya Sofra Weiss

DNA-Protein Complex Crucial To Spread Of Antibiotic Resistance Among Bacteria Solved. Xanya Sofra Weiss

Researchers have solved the structure of a DNA-protein complex that is crucial in the spread of antibiotic resistance among bacteria. Knowing this structure also provides fundamental insight into how cells successfully divide into two new cells with intact DNA.

Xanya Sofra Weiss

Xanya Sofra Weiss

Cytological effects of 60 Hz magnetic fields on human lymphocytes in vitro: sister-chromatid exchanges, cell kin and mitotic rate. Xanya Sofra Weiss

Incubation for 72 h of human peripheral blood cultures in the presence of 60 Hz sinusoidal magnetic fields (MF) magnetic flux densities of 1.0, 1.5, and 2.0 mT led to stimulation of lymphocyte proliferation but had no influence frequency of sister-chromatid exchanges (SCE). The cytotoxic potential of MF combined with the mutagen Mito also was analyzed. An opposite effect between MF exposure and Mitomycin-C treatment in terms of cell kinetics mitotic rate was found, whereas no variation in SCE frequency was observed for this coexposure condition.

Xanya Sofra Weiss

Xanya Sofra Weiss

Cell Signalling Pathways. Xanya Sofra Weiss

Cells use a large number of clearly defined signalling pathways to regulate their activity. In this module, attention is focused on the ON mechanisms responsible for transmitting information into the cell. These signalling pathways fall into two main groups depending on how they are activated. Most of them are activated by external stimuli and function to transfer information from the cell surface to internal effector systems. However, some of the signalling systems respond to information generated from within the cell, usually in the form of metabolic messengers. For all of these signalling pathways, information is conveyed either through protein–protein interactions or it is transmitted by diffusible elements usually referred to as second messengers. Cells often employ a number of these signalling pathways, and cross-talk between them is an important feature. In this section, attention is focused on the
properties of the major intracellular signalling pathways operating in cells to regulate their cellular activity.
During the processes of development, specific cell types select out those signalling systems that are suitable to control their particular functions. One of the aims of this website is to understand how these unique cell-specific signalsomes function to regulate different mammalian cell types.

Xanya Sofra Weiss

Xanya Sofra Weiss

Phosphorylation meets nuclear import: a review. Xanya Sofra Weiss

Phosphorylation is the most common and pleiotropic modification in biology, which plays a vital role in regulating and finely tuning a multitude of biological pathways. Transport across the nuclear envelope is also an essential cellular function and is intimately linked to many degeneration processes that lead to disease. It is therefore not surprising that phosphorylation of cargos trafficking between the cytoplasm and nucleus is emerging as an important step to regulate nuclear availability, which directly affects gene expression, cell growth and proliferation. However, the literature on phosphorylation of nucleocytoplasmic trafficking cargos is often confusing. Phosphorylation, and its mirror process dephosphorylation, has been shown to have opposite and often contradictory effects on the ability of cargos to be transported across the nuclear envelope. Without a clear connection between attachment of a phosphate moiety and biological response, it is difficult to fully understand and predict how phosphorylation regulates nucleocytoplasmic trafficking. In this review, we will recapitulate clue findings in the field and provide some general rules on how reversible phosphorylation can affect the nuclear-cytoplasmic localization of substrates. This is only now beginning to emerge as a key regulatory step in biology.

Xanya Sofra Weiss

Xanya Sofra Weiss

Nuclear Shp-2 keeps telomerase reverse transcriptase in the nucleus – new potential anti-aging target

Vascular diseases are associated with cellular aging, which is accompanied by telomere shortening counteracted in the nucleus by telomerase reverse transcriptase (TERT). Under conditions of oxidative stress TERT is exported from the nucleus and this export is mediated by Src-kinases via tyrosine phosphorylation of TERT. Nuclear export of TERT resulted in accelerated aging of endothelial cells. Therefore, the aim of this study was to determine a counterplayer for nuclear export of TERT.
In embryonic fibroblasts deficient in Src, Fyn and Yes, TERT nuclear export induced by oxidative stress is abolished. Fyn does not seem to play a role, because unlike Src and Yes it is not found in the nucleus. A putative regulator of this export is the tyrosine phosphatase Shp-2, which can regulate the activity of the Src-kinase family. We demonstrated that Shp-2 is localized in the nucleus and associated with TERT in endothelial cells. Overexpression of Shp-2 inhibited oxidative stress induced nuclear export of TERT and ablation of Shp-2 by siRNA reduced nuclear telomerase activity. This inhibition was dependent on the enzymatic activity of Shp-2 and on tyrosine 707 in TERT because overexpression of the dominant negative Shp-2 mutant (C459S) led to a reduction of TERT protein and telomerase activity, whereas telomerase activity in TERTY707F overexpressing cells was not altered by Shp-2. Thus, tyrosine 707 seems to be a critical target for regulation of TERT localization by Shp-2 mediated dephosphorylation. To establish a causal link between Shp-2, nuclear TERT and oxidative stress, we determined reactive oxygen species (ROS) formation in endothelial cells. Overexpression of Shp-2(C459S) (2.45 fold +/- 0.34 of Shp-2 wt) or ablation of Shp-2 by siRNA increased ROS levels (2.23 fold +/- 0.54 of scrambled siRNA). In contrast, keeping TERT in the nucleus by mutating tyrosine 707 or overexpressing Shp-2 wt reduced ROS formation (0.73 and 0.75 fold, respectively).
In summary, these data indicate that TERT is associated with nuclear Shp-2, Shp-2 acts as a negative regulator for nuclear export of TERT probably via regulating tyrosine 707 dephosphorylation of TERT and reducing ROS formation.
Thus, increasing nuclear Shp-2 activity could be a useful tool to delay vascular aging processes.

Xanya Sofra Weiss

Xanya Sofra Weiss